1. Technical Field
The present invention relates to elastomeric laminates comprising more than 3 layers of diene rubber composition, intended in particular to be used in a tire.
2. Related Art
A tire usually comprises a tread, two sidewalls, two beads, a carcass reinforcement passing into the two sidewalls and anchored to the two beads, and a crown reinforcement arranged circumferentially between the tread and the carcass reinforcement. The tread is intended to come into contact with the surface on which the tire runs. The tire may also comprise a tread underlayer, the underlayer being arranged circumferentially between the tread and the carcass reinforcement, preferably between the tread and the crown reinforcement, the tread underlayer being generally adjacent to the tread.
In the tire, the tread underlayer must adhere to the tread sufficiently in order to avoid the underlayer at the surface of the tread from detaching from the tread for the entire life of the tire. The underlayer generally adheres to the tread by means of physical or chemical phenomena, such as phenomena of interpenetration, entanglement or crosslinking of the diene rubber compositions constituting the tread and the tread underlayer, respectively.
Under the conditions suitable for processing and curing diene rubber compositions placed in contact with one another, these compositions are solidly bonded together and the complex obtained makes it possible to withstand the stresses associated with the field of application in question, especially that of tires.
The compositions which may be used in a tread may contain an elastomer matrix which has a low degree of unsaturation or which comprises a terpolymeric elastomer of ethylene, of an α-olefin and of a non-conjugated diene. An elastomer matrix is considered to have a low degree of unsaturation when it contains less than 10% by weight of diene units. Generally, the rubber composition of a tread underlayer is generally based on an elastomer matrix which comprises natural rubber, considered to be a highly unsaturated elastomer. However, the level of adhesion between, on the one hand, a first composition based on an elastomer matrix which has a low degree of unsaturation or which contains a terpolymeric elastomer of ethylene, of an α-olefin and of a non-conjugated diene, and, on the other hand, a second composition based on an elastomer matrix containing a highly unsaturated elastomer, may be deemed to be insufficient, especially for an application, in tires, of the first composition as tire tread and of the second composition as tread underlayer.
To overcome this, it is possible to use a material which will serve as bonding rubber or adhesive for bonding between the first composition and the second composition, especially used, respectively, as tire tread and tread underlayer. In this case, the tread underlayer is no longer adjacent over its entire length to the tread, but is separated therefrom by the bonding rubber.